Botulinum toxin chemodenervation for childhood strabismus in England: National and local patterns of practice

Long-Term Effects of Botulinum Toxin A for Horizontal Concomitant Strabismus in Chinese Children

INTRODUCTION

For childhood strabismus, early surgical intervention improves both motor and sensory outcomes. Botulinum toxin type A (BTX-A) injection is an alternative to incisional surgery that is fast, less invasive, and preserves a more normal biomechanical construct. This study was undertaken to assess the safety and effectiveness of BTX-A for horizontal concomitant strabismus in children in our institution.

PATIENTS AND METHODS

Records of all children less than age 18 years with follow-up at least 12 months who were treated with BTX-A for horizontal concomitant strabismus at Beijing Children's Hospital between December 2014 and February 2021 were reviewed retrospectively. Bilateral injections of BTX-A (Henli, 1.25 IU to 5 IU/0.1 ml) were made into the medial or lateral rectus muscles according to the angle of deviation. Reinjection was permitted if the initial alignment was not satisfactory within 1 to 6 months post-injection. Motor success was defined as a final misalignment ≤10 PD. Sensory success was defined as the presence of any evidence of sensory fusion, distance stereopsis, or near stereopsis at the last visit.

RESULTS

Seventy-one patients were included. Fifty-two had esotropia, and 19 had exotropia. There was a significant decrease in the angle of deviation in all treated patients. The overall motor success rate was 60.6%. The motor success rate was highest in children with esotropia <50 PD (81.5%). Motor success was better for children with partially accommodative esotropia and acquired non-accommodative esotropia (80%, 83.3%, respectively) than for children with infantile esotropia (47.4%). Compared with the esotropia group, the fusion was significantly higher in the exotropia group (p = .007), and the proportion of patients with stereoacuity of better than 100 sec arc was higher also in the exotropia group (71.4%, p = .007), evidence of sensory outcomes were significantly better in the exotropia group. Complications were few. Twenty patients (28.2%) developed transient ptosis after injections; transient vertical deviations were seen in 3 patients (4.2%); and subconjunctival hemorrhage was seen in 5 patients (7%).

CONCLUSIONS

BTX-A appears to be an effective treatment for the management of horizontal strabismus with motor outcomes best in children with acquired smaller-angle esodeviations. Children with exodeviations had better sensory outcomes in this cohort. A randomized controlled study comparing incisional surgery to BTX-A will be important for guiding future treatment decisions.

Factors Affecting the Efficacy of Botulinum Toxin Injection in the Treatment of Infantile and Partially Accommodative Esotropia

PURPOSE

We aimed to investigate the effect of botulinum toxin (BT) injection on the treatment of infantile and partially accommodative esotropia (PAET).

METHODS

This retrospective cohort study included patients who received BT injections for infantile and PAET between January 2015 and December 2018. Treatment was considered successful if orthotropia, consecutive exotropia, or esotropia within 10 prism diopters (PD) was achieved.

RESULTS

The overall success rate was 47.4%, with a mean follow-up period of 27.8 months in 403 children. BT treatment was considered successful in 37.1% of cases of infantile esotropia and 53.1% of cases of partially accommodative esotropia. The average deviation angle before starting treatment was 35.5 ± 13.9 PD. Side effects 1 week after BT injections included transient overcorrection (63.8%) and transient ptosis (41.7%). There were no significant differences in the success rates between the different doses of BT (P = 0.69). The angle of deviation at presentation was significantly associated with the success rate of BT injection (failed group, mean: 38.1 ± 15.3 PD vs. success group, mean: 32.6 ± 11.6 PD; P < 0.001). Other factors associated with higher success rates were overcorrection at 1 week and PAET, while multivariate logistic regression analysis showed that a smaller angle of deviation and overcorrection (1 week after injection) were associated with a higher success rate.

CONCLUSION

A smaller angle of deviation and transient overcorrection were associated with a higher success rate, and no significant difference was observed in the success rates of different BT doses.

Conventional surgery versus botulinum toxin injections for partially accommodative esotropia

PURPOSE

To compare the effect of botulinum toxin injection (BTX) to bilateral medial rectus recession (BMR) in partially accommodative esotropia (PAET).

METHODS

The medical records of children 1-14 years of age treated for PAET with BMR or BTX between 2010 and 2020 at a single institution were reviewed retrospectively. PAET was defined as residual esotropia of at least 14^Δ after 6 weeks of continuous wear of full cycloplegic refraction (> +2.5 D). Success was defined as esotropia of 0^Δ-10^Δ after a single surgery or ≥1 BTX injections.

RESULTS

Of 224 patients, 121 received BTX and 103 underwent BMR. BMR showed a higher success rate than BTX (70.9% vs 53.7% [P = 0.006]). BMR was more successful in males, in patients >5 years of age, and when spherical equivalent was ≤ +5.00 D (79.2%, 74.3%, and 67.5%, resp. [P < 0.05]). Mean follow-up was shorter in the BMR group than in the BTX group (16.7 ± 14.7 vs 31.4 ± 29.5 months [P = 0.0001]). Mean duration of surgery was significantly shorter in the BTX group (5.2 ± 4.3 vs 70.5 ± 31.4 min [P = 0.0001]). Postoperative inferior oblique overaction was more common in the BTX group (7.4%; P = 0.02 [Fisher exact test]), and persistent ptosis was only seen in the BTX group (0.8%); consecutive exotropia was only seen in the BMR group (2%).

CONCLUSIONS

In our study cohort, BMR had a higher success rate than BTX. Conventional surgery allowed for shorter follow-up and fewer complications than BTX in the treatment of PAET.

Success rates of botulinum toxin in different types of strabismus and dose effect

OBJECTIVE

To determine the effect of botulinum toxin in different types of strabismus and analyze its dose effect.

DESIGN

This was an interventional clinical study performed in a tertiary care university hospital.

METHODS

Eighty six patients treated with botulinum toxin for strabismus were included. Main outcome measures involved success of botulinum toxin, alignment change per unit of toxin, and dose effect on complications and outcomes.

RESULTS

Success rates were 31% for infantile esotropia, 25% for partially accommodative esotropia, 61.5% for residual esotropia, 25% for third cranial nerve paralysis, 13.3% for sixth cranial nerve paralysis, 75% for Duane retraction syndrome, and 38.5% for nonaccomodative esotropia. Improvement in deviation size after botulinum toxin treatment was significant in patients with infantile esotropia (p = 0.001), residual esotropia (p = 0.001), and nonaccomodative esotropia (p = 0.03). Mean deviation change per 1 unit of toxin was 2.7 ± 2.4 prism diopters (PD) with a single injection and 2.1 ± 1.9 PD with multiple injections. A 3.32 PD of early deviation change with botulinum toxin corrected 1 PD of final deviation. Success rate was not correlated with age (r = 0.040, p = 0.8), sex (r = -0.083, p = 0.6), mean dose (r = -0.149, p = 0.35), or total dose (r = 0.165, p = 0.29) but was significantly correlated with deviation size (β = -0.077, p = 0.0001). Complications were not associated with the dose of botulinum toxin (p > 0.05).

CONCLUSIONS

Botulinum toxin has variable outcomes in different types of strabismus. Still, it reduces the deviation size in most patients, thus allowing for a smaller amount of subsequent muscle surgery. Early overcorrection is a more powerfull indicator of better outcome than postinjection duction deficit.

Comparing Botulinum Toxin Injections with Extraocular Muscle Surgery in Toddlers with Esotropia: A Retrospective Analysis

BACKGROUND

In toddlers with esotropia, early alignment of the visual axes either with extraocular muscle surgery (EOMS) or botulinum toxin injections (BTIs) into both medial rectus muscles may result in improved depth perception. We compared the outcome of BTIs with EOMS in toddlers in order to gain further insight into the advantages and disadvantages of either method.

PATIENTS AND METHODS

In this retrospective study, our encrypted database was searched for toddlers with esotropia aged 35 months or younger at the time of initial treatment with either BTIs or EOMS and who had a follow-up of at least 2 years. We analyzed the angle of deviation, dose effect (DE), and binocularity as well as the number of interventions.

RESULTS

We identified 26 toddlers who received their first treatment for esotropia within the first 35 months of life: 16 with BTIs (9 males, 7 females) and 10 with EOMS (3 males, 7 females). Mean follow-up was considerably longer in the EOMS (87.7 months) than in the BTI group (35.7 months). Age at first intervention was 22.8 months in the BTI and 24.1 months in the EOMS group, and each toddler wore its full cycloplegic refraction. Mean angle at treatment was 41.25 prism diopters (PD) in the BTI compared to 52.9 PD in the EOMS group. The BTI group received an average of 1.68 BTIs, with a mean dosage of 14.5 IU Botox and a mean DE (mDE) of 1.8 PD/IU. In the EOMS group, the average number of surgeries was 1.4, with a mean dosage of 16.85 mm and a mDE of 3.14 PD/mm surgery. Some degree of binocularity could be observed in 9 (56%) of the BTI (5 × Bagolini positive, 2 × 550″, 2 × 220″) and in 4 (40%) of the EOMS group (2 × 3600″, 1 × 550″, 1 × 300″). By the end of the BTI group follow-up, four toddlers electively underwent EOMS rather than a 3rd BTI (followed by a 3rd BTI in 1), which resulted in the appearance of measurable binocularity in all four (1 × Bagolini positive, 1 × 220″, 1 × 200″, 1 × 60″).

CONCLUSIONS

Our results show that BTIs are a viable treatment alternative in early esotropia. Even if EOMS is ultimately required, some binocularity may develop as the visual axes are aligned for some time in the sensitive phase owing to the effects of Botox. Moreover, less surgical dosage is needed than would have otherwise been necessary to treat the original angle of deviation. BTIs are faster, less invasive, and present as an effective alternative when patient compliance is too low to reliably measure the angle of deviation, which is essential for the planning of EOMS.

The Efficacy of Dose Increments of Botulinum Toxin A in the Treatment of Childhood Esotropia

Background

Botulinum toxin is known to have a powerful chemodenervation effect, and it is a well-established alternative to incisional surgery for strabismus. This study aims to investigate the efficacy of dose increments of botulinum toxin A (BTA) for the treatment of specific ranges of angle deviation.

Methods

This was a prospective study that included patients presenting with esotropia to Dhahran Eye Specialist Hospital between 2016 and 2020, who were managed by a single surgeon. Botulinum toxin was given in different dosages (2.5, 5, 7.5, 10 international units (IU)) according to the size of deviation (11–19, 20–29, 30–39, and ≥40 prism diopters (PD)), respectively. A successful outcome was defined as deviation ≤10 PD in the last visit (a minimum of 6 months) following a single injection.

Results

A total of 56 patients with esotropia were included. The mean pre-treatment angle of deviation was 38.6 ± 2.5 PD. BTA injection in a dose of 2.5 IU for the 11–19 PD angle of deviation showed the highest rate of successful outcomes (75%). According to the type of esotropia, partially accommodative esotropia showed the best response to the use of dose increments (59%). The incidence of ptosis post-BTA injection was the least (37.5%) with the smallest dose (2.5 IU).

Conclusion

BTA usage in dose increments is safe, efficient, and might be more cost-effective with less incidence of BTA associated complications. Different esotropia diagnoses have different clinical responses. However, larger studies are necessary to better predict the outcome of using dose increments.

Outcomes of pediatric accommodative esotropia with botulinum toxin A treatment in Thailand

Accommodative esotropia is a condition commonly encountered by pediatric ophthalmologists. Patient with accommodative esotropia wear hyperopic glasses to decrease accommodation which occasionally provide them with good vision without glasses. Children are known to have limited compliance with glasses and patching. Their limited cooperation can also lead to variability in angle measurement across visits and defer surgery. To cope with these challenges, our team offered botulinum toxin injection to the medial rectus as an optional treatment while waiting for compliance and deferring the surgery. This is retrospective study including data from 114 accommodative esotropia patients who were injected with botulinum toxin into the medial rectus between 2010 and 2017. Of these, 102 patients met the inclusion criteria. Almost half of the patients were boys (47.06%). The average angle deviation before injection was 40 prism diopters (PD). The post-injection angle averaged at 11 PD at 2 weeks, 19 PD at 3 months, and 25 PD at 6 months. At 6 months, 51 patients (50.00%) had satisfactory results, 17 (16.67%) had excellent results (ortho to esotropia < 10 PD) and 34 (33.33%) had small angle esotropia (esotropia 11-20 PD). All complications including ptosis (37.25%), exotropia (11.76%), and hypertropia (4.9%) were reversible. Botulinum toxin injection into the medial rectus for pediatric esotropia showed satisfactory outcomes in 50% of patients with minimal complications. The study showed no significant association of good outcomes with age at onset, age during injection, status of development, status of amblyopia, refractive error, and angle of deviation as analyzed by the statistical package for social sciences.

Essential Infantile Esotropia: A Course of Treatment From Our Experience

Background: Essential infantile esotropia (EIE) is the most common type of childhood esotropia. Although its classical approach is surgical, less invasive techniques have been proposed as an adjunct or alternative to traditional surgery. Among them, chemodenervation with botulinum toxin (BT) has been investigated, showing variable and sometimes conflicting results. Objectives: To compare the outcomes of bilateral BT injection and traditional surgery in a pediatric population with EIE in order to optimize and standardize the therapeutic approach. Other purposes are to evaluate whether early intervention may prevent the onset of vertical ocular deviation (which is part of the clinical picture of EIE) and/or influence the development of fine stereopsis, and also to assess changes in refractive status over time among the enrolled population. Methods: A retrospective consecutive cohort study was conducted in 86 children aged 0-48 months who underwent correction of EIE. The primary intervention in naïve subjects was either bilateral BT injection (36 subjects, "BT group") or strabismus surgery (50 subjects, "surgery group"). Results: Overall, BT chemodenervation (one or two injections) was effective in 13 (36.1%) subjects. With regard to residual deviation angle, the outcomes at least 5 years after the last intervention were overlapping in children receiving initial treatment with either injection or surgery; however, the success rate of primary intervention in the surgery group was higher, and the average number of interventions necessary to achieve orthotropia was smaller. Both early treatment with chemodenervation and surgery at a later age were not found to prevent the onset of vertical ocular deviation, whereas, surprisingly, the percentage of subjects developing fine stereopsis was higher in the surgery group. Finally, with regard to the change in refractive status over time, most of the subjects increased their initial hyperopia, whereas 10% became myopic. Conclusions: Our data suggest that a single bilateral BT injection by age 2 years should be considered as the first-line treatment of EIE without vertical component; whereas, traditional surgery should be considered as the first-line treatment for all other cases and in subjects unresponsive to primary single BT injection.

Long-Term Effects of Botulinum Toxin in Large-Angle Infantile Esotropia

Purpose

The purpose of this study is the motor outcome analysis of early Botulinum toxin (BT) treatment in patients affected by large-angle infantile esotropia (IE).

Patients and Methods

Retrospective analysis of 130 medical charts of IE patients who underwent BT injections between 2004 and 2019 was performed. All patients underwent BT injections within 13 months of age.

Results

Thirty patients, matching the inclusion criteria, were included in the study. Twenty-eight patients showing residual ET ≥25 PD (34.3±6.6 PD ranged from 25 to 50) underwent surgery.

Conclusion

Our result after 1 Botulinum toxin injection showed a very low success rate (6.7%) at last follow-up (28.3±7.2 months). Our data would suggest one Botulinum toxin injection in children affected by large-angle infantile esotropia allows a significant reduction of deviation but does not avoid the need for surgical treatment.

Insights Into the Role of Exposed Surface Charged Residues in the Alkali-Tolerance of GH11 Xylanase

Thermostable and alkaline- or acid-stable xylanases are more advantageous in agricultural and industrial fields. In this study, a rational structure-based design was conducted based on a thermostable GH11 xylanase TlXynA from Thermomyces lanuginosus to improved pH-tolerance. Four mutant enzymes (P1, P2, P3, and P4) and five variants (N1, N2, N3, N4, and N5) were constructed by substituting surface charged residue combinations using site-directed mutagenesis. Compared to the native enzyme, two mutants P1 and P2 showed higher acid tolerance, especially at pH 3.0, presented 50 and 40% of their maximum activity, respectively. In addition, four mutants N1, N2, N3 and N4 had higher tolerance than the native enzyme to alkaline environments (pH 7.0-9.0). At pH 9.0, the residual activities of N1, N2, N3, and N4 were 86, 78, 77, and 66%, respectively. In summary, an improved pH-tolerance design principle is being reported.

The Use of Botulinum Toxin in Strabismus Treatment

There is a long and extensive experience with the use of Botulinum Toxin type A (BoNT-A) injection in the treatment of different types of strabismus and oculomotor palsies. The frequency of its use varies depending on the country and institution. It is a short procedure, may reduce general anesthesia exposure, causes minimal scarring compared to surgery, and can be proposed as an early treatment in unstable strabismus. Over many years, the experience of using BoNT-A indications has been refined and new applications have been reported. The use of BoNT-A in the postoperative period, after strabismus surgery or during surgery, can also be beneficial.